This invention relates to concentrated humic acid which is formed from a humic acid bearing ore, and to the process of producing the humic acid.
Soil humus is known as an important soil constituent for enhancing growth in plants. However, the humus content of many soils is inadequate and, in those cases, it is desirable to increase the humus content of the soil by treating it with various organic matter. It has been found that humic acids also increase the efficiency of soil applied fertilizers. This is accomplished through the high cation exchange capacity of humus which is in the range of 200 to 500 meg per 100 grams at pH 7. This is in comparison to soils which have cation exchange capacities that usually range from 8 to 45 meg per 100 grams at pH 7. A decreased cation exchange capacity is undesirable because it has the capacity to tie up fertilizer and keep it from being utilized by the plant. It is thus readily apparent that humus with its relatively high cation exchange capacity increases the efficiency of fertilizer.
One approach to improving the humus content of the soil has been to extract humus acid from humus acid bearing minerals and then apply the extracted humus acid in a concentrated form to the soil. One example of this approach is disclosed in U.S. Pat. No. 3,111,404 and U.S. Pat. No. 3,544,296, issued to John C. Karcher. These patents relate to the treatment of humic acid bearing ores, such as leonardite, to form a granular ammonia humate fertilizer. However, in these patents, the complexity of the process to form the humic acid concentrate is such that the end product formed is relatively expensive and the process itself employes expensive and complex machinery. Also, the end product in the Karcher patents is granular and not a concentrated liquid, which form would facilitate storage, shipment and handling in actual use, such as by permitting direct application of the humic acid to the soil through an irrigation system or by crop dusting. Also, in the Karcher process, other elements which might benefit plant life, such as metallic trace elements are removed because mechanical separation is employed to separate undissolved leonardite constituents.
In Karcher, phosphoric acid is first added during the process to convert the metallic salts of humic acid to humic acid, then ammonia is later added to form ammonium humate, which is then filtered to separate it from the solids present. The ammonium humate liquid is then dried to form a solid ammonium humate, and to reduce the pH of the product to 7. This drying procedure is time consuming, requires significant power and requires additional equipmemt to accomplish it. Also, during the Karcher process, the pH may be so low that constituents that may be beneficial to plant life may be lost.
Another process for extracting humic acid from a humic acid bearing ore is disclosed by U.S. Pat. No. 3,770,411 to James C. Chambers, et al. In that patent, the process requires the addition of ammonia and phosphoric acid in a first and second mixture, respectively. In U.S. Pat. No. 3,398,186 to Nelson N. Schwartz, et al, a process of extracting humic acid is disclosed wherein an aqueous solution of a sulfate salt selected from the group consisting of sodium sulfate, potassium sulfate and ammonium sulfate is used as the extracting solution. Schwartz, et al discloses that a caustic soda extracting solution may be used wherein the mixture is heated under reflux conditions for 24 hours and thereafter the solution is cooled and acidified resulting in a dark precipitate of humic acid. Similarly, in U.S. Pat. No. 3,076,291 to Frank Gardner, ammonium hydroxide, potassium hydroxide or sodium hydroxide may be used in a method for making a seed germination promoter. In U.S. Pat. No. 3,222,160 to Yves Ramus, a process for manufacturing a humic fertilizer is disclosed wherein a cellulosic containing material is impregnated with a solution of nitric acid which, in turn, is reacted with a compound selected from the group consisting of ammonia, potash and lime.